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Imaging Analysis As part of the acquisition quality control for this data, fused SPECT-CT images were checked for proper registration of attenuation maps and emission data. SPECT-CT transaxial fusion SPECT-CT sagittal fusion

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Further quality control checks showed the acquisition to be of good quality: The stress and rest selective linograms showed no significant motion in the vertical direction and showed no significant extra-cardiac activity that would interfere with the reconstruction. The stress and rest sinograms showed no significant motion in the horizontal direction Myocardial count density was adequate. The stress maximum pixel value was 201; rest maximal pixel value was 65. The guideline for an adequate count study for projection images is to have a maximum pixel value of at least 50 counts within a tight circular/ elliptical ROI around the epicardial edge of the myocardium on an anterior view of the heart. There were no gating errors

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The correct answer is C - Gating errors Thickening is the parameter most prone to error in the presence of arrhythmias. Slice appearance is maintained in the presence of arrhythmias except in very severe cases. LV ejection fraction (EF) is a robust parameter that is little affected by arrhythmias. Quantitative perfusion measures were also little affected by arrhythmias except in the case of atrial fibrillation. 1 As has been well documented in the literature, vertical and horizontal motion and myocardial count density are critical for slice image quality. Intense visceral activity close to the heart can also affect slice image quality as it results in changed slice count densities.

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The rotating projection images show soft tissue attenuation in the waist area which can cause increased attenuation of the inferior wall. Stress projection images Rest projection images Soft tissue attenuation may create artifacts that mimic true perfusion abnormalities and can lead to false positive interpretation. Click

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Question 2 – Attenuation correction What are the advantages of doing attenuation correction on cardiac studies? A.Provide images that are more uniform and easier to interpret B.Decrease acquisition time C.Increase myocardial count density D.Increase sensitivity and overall diagnostic accuracy E.Both A and D

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The correct answer is E – Both A and D The diagnostic accuracy of SPECT imaging is compromised by soft tissue attenuation artifacts. Though education, experience, and the application of gated SPECT imaging have greatly helped, there is a need for improved diagnostic accuracy. Attenuation correction can provide images that are more uniform and easier to interpret, and increase sensitivity and overall diagnostic accuracy. Attenuation correction SPECT techniques represent a significant advance in myocardial perfusion imaging and hold great promise for improved assessment of cardiac patients. 2

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Question 3 – CT-based attenuation correction What are the further advantages of doing CT-based attenuation correction on cardiac studies? A. CT-based AC produces high quality transmission maps B. CT-based AC is consistent with time C. CT-based AC is consistent over a full range of body types D. All of the above

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The correct answer is D – all of the above There are significant differences in the ability of different commercial AC systems to reduce artifacts due to attenuation, hot liver / bowel activity and type of orbit. Systems that can generate high quality attenuation maps yielded the best results. A high quality attenuation map appears to be an important determinant of image quality. 3 Stress attenuation mapRest attenuation map

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EKG Results Non-specific ECG changes were noted with no ST depression at maximal exertion. Test terminated at maximal heart rate and SOB. No chest pain was noted. Findings FBP images were interpreted as inferior wall scar with possible ischemic component. This could also be a diaphragmatic attenuation artifact. With CT- based AC the inferior wall is shown to be viable with no ischemia. The validity of the revascularization of the RCA is confirmed. Findings and Images Courtesy of VA Medical Center, Baltimore, Maryland For more information on GE Nuclear Cardiology products and the unique Hawkeye CT based cardiac AC, visit: GE Hawkeye Cardiac Attenuation CorrectionGE Hawkeye Cardiac Attenuation Correction